Cellulose-ester composition



PATENT OFFICE.

UNITED STATES JOHANNES M. KESSLER, OF WEST ORANGE, NEW JERSEY, ASSIGNORTO E. I. DU FONT DE NEMOURS COMPANY, OF WILMINGTON, DELAWARE, ACORPORATION OF Patented Nov. 30, 1920.

DELAWARE.

CELLULOSE-ESTER COMPOSITION.

1,360,759, Specification of Letters Patent.

No Drawing.

To all whom it may concern.

Be it known that I, JoHANNns M. KEssLER, a citizen of the United States,and a resident of West Oran e, in the county of Essex and State of Newersey, have invented a certain which some or all of the camphorordinarily present is replaced by acetylated glycerol which issubstantially free from glyceryl monoacetate (mono-acetin) and fromacetic acid, and which contains preferably,'more than of glyceryltriacetate (triacetin), the remainder being glyceryl diacetate.

The application of the commercial acetate of glycerin, (known as acetin)as a solvent or colloiding agent for pyroxylin was patented as long agoas 1889 by Schiipphaus in Patent 410208, and is included as part of theinvention in the provisional specification of British Patent 13,131 of1900 to Goldsmith. In more recent years patents have been grantedcovering its use in connection with cellulose acetate. Although knownfor so many years acetin has never found, as far as I know, practicalapplication in the pyroxylin industry.

The main objection to the use of acetin, and'one which accounts for itshaving been discarded by manufacturers as a substitute viscous pyroxylinsolutions and of solid compounds possessing great flexibility. I have,however, found that in atmospheres heavily charged with moisture thesecompounds may become covered with water, owing to the hygroscopic-natureof the acetins.

The remedy which Schiipphaus proposes is to introduce the radical of anacid other than Application filed June 19, 1920. Serial No. 390,133.

acetic acid into the acetins. Although the resulting mixed esters may bean improvement over commercial acetin in not being so hygroscopic, theyalso as far as I know have not found practical application, 1111-doubtedly due to their more complicated method of manufacture and theirrelatively high cost.

My researches have now made clear the following facts:

The commercial acetate of glycerol consists of a mixture of mono, di,and tri acetin. The mono-acetin is a very hygroscopic product, easilysoluble in water; diacetin, although less hygroscopic, is quite solublein water; Whereas triacctin is the least soluble. Owing to the fact thatmono-acetin readily absorbs moisture from the atmosphere, it isobviously not suitable for use in pyroxylin compounds, particularlypyroxylin solutions, as it forms a white film. Diacetin absorbs moistureto a less degree and when used alone also gives a white film, but whenused with a sufficient amount of triacetin produces a transparent film.It can, therefore, easily be seen why commercial acetate of glycerol hasnot been found of practical im ortance in the pyroxylin industry.

11 carrying out experiments to ascertain the possible utility of acetinsubstantially free from mono-acetin, I found that such an acetincontaining more than-75% of triacetin yielded a plastic that was freefrom the objectionable features that ordinarily resulted from the use ofcommercial acetins. As the result of further investigation, I have nowdiscovered that for many purposes an acetin containing'much less than75% of, but preferably more than 50%, triacetin, can be employed as asoftener in cellulose ester compositions, and particularly 1n connectionwith pyroxylin plastics, provided care is taken to exclude mono-acetinand free acetic acid.

My invention may be illustrated by the following example I A mixture of100 parts of pyroxylin, preferably anhydrous, about parts by weightofdenatured alcohol, and about 28 partsof acetin free from mono-acetin,and COIlttLHh ing about of triacetin, is kneaded, preferably at anelevated temperature of from 40 to 55 (1, until properly colloided,after which it is put on the rolls and through the pressing, sheetingand seasoning which are well known in the manufacture of cellulosenitrate plastics, such as pyralin, celluloid,

etc. Suitable amounts of stabilizer, for example, urea, pigments andcolors may be 7 added either during the mixing or the rollacetic acidand an alkyl acetate,

ing operation. The proportion of the ingredients given above may bevaried within certain limits. Also other solvents, such as wood alcohol,acetone, etc., may be used in place of denatured alcohol. If a certainamount -of camphor or another camphor substitute besides acetinis used,the amount of acetin necessary for proper colloiding is decreased;preferably the total amount of camphor and camphor substitutes includingthe acetin is not more than 31 parts for about 100 partsof-nitrocellulose.

The acetin which can be used may, as indicated above, vary considerablywith respect to the ratio of diacetin to triacetin.

but ordinarily the triacetin content should be above 50%. The ratio ofcellulosenitrate to softener' may also vary to some extent, as forexample, from 4:1 to 3:1; beyond these limits a satisfactory plastic isobtainable only with diificulty.

n acetin substantiallyfree from monoacetin and acetic acid and suitablefor my pupose may be made as follows:

lycerol (1 mol.) is treated with glacial (5 to 6 mols.) and 0.1%sulfuric acid as catalyze'r, and there is distilled ofi',

through a very efiicient fractionating' column, in the form of diluteacetic acid, the water formed during the reaction, until the strength ofthe acid coming over reaches or more. After neutralizing the catanddistilling off the excess sible at ordinary pressure, the residue isthen subjected. to fractional distillation in vacuum, yielding a finalneutral product with more than 60% triacetin.

Liquid coating compositions may be made from the above sufiicientsolvent, for example methyl alcoho such as ethyl or amyl acetate toproduce a thin or a viscous solution. l3y flowing the viscous solutionon to smooth-surfaces, sheets or films having. very desirable propertiesare readily obtained,

' after evaporation of the solvent.

I claim: 1. A composition containing a cellulose described plastics byadding nitrate and an acetin substantiallv free from .mono-acetinand-from free acetic acid.

2. A composition containing a cellulose nitrate and an acetinsubstantially free from mono-acetin and containing at least 50% oftriacetin.

3. A composition consisting essentially 'of cellulose nitrate and asoftener comprising acetin substantially free from monoacetin andcontaining at least 50% of triacetin, the ratio of said cellulosenitrate to said softener being from about:3:1t0 4:1.

4. A composition consisting essentially. of cellulose nitrate and asoftener comprising camphor and an acetin substantially free frommono-acetin.

5. A composition consisting essentially of cellulose nitrate and asoftener comprising camphor and an acetin substantially free frommono-acetin and containing at least 50% of triacetin.

6. A composition consisting essentially of cellulose nitrate and asoftener 'comprising camphor and an acetin substantially free frommono-acetin, the ratio of said cellulose nitrate .to said softener beingabout 3:1.

7. A composition consisting essentially of cellulose nitrate and asoftener'comprising camphor and an acetin substantially free frommono-acetin and containing at least 50% of triacetin, the ratio of saidcellulose nitrate to said softener being about 3:1.

8. A composition consisting essentially- 70% of triacetin. of freeacetic acid as far as pos- I 9. A composition consisting essentially ofcellulose nitrate and a softener comprising camphor and acetinsubstantially free from mono-acetin, said acetin containing from aboutAOto 30% of diacetin, and from about to 70% of triacetin,'the ratio ofsaid cellulose nitrate'to said softener being about '3 1.

10. A composition consisting essentially of cellulose nitrate and&softener comprising camphor and acetin, substantially free frommono-acetin, said acetin containing from about 40 to 30% of. diacetin,and from about 60 to 70%oftriacetin.

In testimon whereof I aflix 111 Si ature.

J HANNES M.K S

